UC Davis UC Davis Previously Published Works Title Relationship Between Historical Lameness, Medication Usage, Surgery, and Exercise With Catastrophic Musculoskeletal Injury in Racehorses. Permalink https://escholarship.org/uc/item/02m8g1wb Journal Frontiers in veterinary science, 5(SEP) ISSN 2297-1769 Authors Hitchens, Peta L Hill, Ashley E Stover, Susan M Publication Date 2018 DOI 10.3389/fvets.2018.00217 Peer reviewed eScholarship.org Powered by the California Digital Library University of California ORIGINAL RESEARCH published: 07 September 2018 doi: 10.3389/fvets.2018.00217 Relationship Between Historical Lameness, Medication Usage, Surgery, and Exercise With Catastrophic Musculoskeletal Injury in Racehorses Peta L. Hitchens 1,2*, Ashley E. Hill 3 and Susan M. Stover 1 1 J.D. Wheat Veterinary Orthopedic Research Laboratory, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States, 2 Equine Centre, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia, 3 California Animal Health and Food Safety Laboratory System, University of California, Davis, Davis, CA, United States Background: The rate of catastrophic musculoskeletal injuries (CMI) in racehorses is high in the United States compared to other countries. Few modifiable risk factors related to lameness, medication, and surgery history have been identified. Objective: To detect management factors that increase risk of CMI by comparing medical histories between horses that sustained, and horses that did not sustain, a CMI. Edited by: Francisco Ruiz-Fons, Study design: Case-control. Consejo Superior de Investigaciones Científicas (CSIC), Spain Methods: Racehorse necropsy data (May 2012-June 2013) were obtained through Reviewed by: the California Horse Racing Board Postmortem Program. Attending veterinarians of Mary Claire Scollay Ward, Thoroughbreds (TB) and Quarter Horses (QH) that experienced CMI, and of three University of Kentucky, United States matched control horses, were invited to complete an online veterinary medical history Agneta Egenvall, Swedish University of Agricultural survey. We investigated associations between CMI and lameness, medication, surgery, Sciences, Sweden and exercise history using multivariable logistic regression. *Correspondence: Results: There were 146 TB (45 cases, 101 controls) and 17 QH (11 cases, 6 controls) Peta L. Hitchens [email protected] surveys completed. TB cases were more likely to show signs of lameness within the 3 months prior to death compared to controls. A high proportion of both cases (64.3%) Specialty section: and controls (76.8%) were administered medications, but unraced TB case horses were This article was submitted to Veterinary Epidemiology and more likely to have been administered systemic medications compared to those that Economics, previously raced. TB cases were more likely to have raced with greater intensity during a section of the journal Frontiers in Veterinary Science their career, but had eased off in the month preceding CMI. For QHs, there was insufficient Received: 04 April 2018 power to detect significant differences between cases and controls that showed signs Accepted: 17 August 2018 of lameness, or that were administered medications. Surgery history was not associated Published: 07 September 2018 with CMI. Citation: Hitchens PL, Hill AE and Stover SM Main limitation: Insufficient power to detect small effect sizes. (2018) Relationship Between Historical Conclusions: The study provides information that can be used to aid in identification of Lameness, Medication Usage, Surgery, and Exercise With horses at high risk for catastrophic injury, and management factors that can be modified Catastrophic Musculoskeletal Injury in to reduce the risk for all horses. Racehorses. Front. Vet. Sci. 5:217. doi: 10.3389/fvets.2018.00217 Keywords: epidemiology, musculoskeletal injury, horse, equine, fatality Frontiers in Veterinary Science | www.frontiersin.org 1 September 2018 | Volume 5 | Article 217 Hitchens et al. Predictors of Racehorse Catastrophic Injury INTRODUCTION (CHRB) Postmortem Program. CAHFS conduct post-mortem examinations of every horse that has died or was euthanized Musculoskeletal injuries are the primary cause of death for at racing or training facilities under the jurisdiction of the racehorses (1–4), and in California, there are about two CHRB. Three control racehorses were selected for each case. For catastrophic musculoskeletal injuries (CMI) for every 1,000 race cases that died as a result of an injury incurred during racing, starts in both Thoroughbred (TB) (5–7), and Quarter Horse controls were selected from unaffected horses that competed in (QH) racing (3, 7). This incidence of CMI is higher than the the same race. For cases that died as a result of an injury incurred incidence reported in other countries such as Australia and New during training, controls were selected from unaffected horses Zealand (0.4/1,000 starts) [(2, 8)], and the United Kingdom that recorded an official timed workout on the same day and (0.7/1,000 starts) (4). California has seen a reduction in the at the same racetrack as their respective case, and matched on frequency of fatalities in recent years (9), with this reduction breed, age (years), and sex (intact male, neutered male, female). credited to the implementation of a Racing Safety Program Career race and officially timed workout reports for each case that has included horseshoe restrictions, improvement of and control horse were obtained from a commercial database of track surfaces, restrictions on injection of some medications official racing industry records (InCompass Solutions Inc., The (e.g., corticosteroids), and continuing education of trainers. Jockey Club, Lexington, KY, USA). From these records, high- Implementation of other factors related to the management of speed exercise history variables were generated using custom the horse should therefore also influence the incidence of such software detailed elsewhere (38, 39). Data were limited to high- injuries. speed exercise performed to the date of death of the respective Risk factors investigated for CMI in racehorses have been case and included variables associated with their career (from well reviewed (10–16). Factors associated with increased risk the first recorded event to death), including number of events of CMI or fatality include horse and race-level characteristics (races and official timed works), time between events, intensity of such as horse age (4, 17–23), age at first start (21–23), horse events, and lay-up (≥60 days without an official recorded event). sex (17, 19, 22, 24, 25), race distance (21–24, 26), type and condition of track surface (4, 20–24, 27–30), class of race (18, Survey 22, 24), and number of race starters (18). Factors related to A three-part 48-question confidential online survey was designed management or training and racing programs that are associated in the open source software LimeSurvey (Supplementary File 1; with CMI include prior racing history (21, 22, 25, 31–33), horse LimeSurvey 2.0, 2013; www.limesurvey.org). The survey was shoe characteristics (e.g., use of toe grabs) (25, 34), and lay- piloted by official veterinarians prior to study commencement. up history or extended intervals since last race (24, 25, 32). Consent was obtained from the attending veterinarian (having Additionally, musculoskeletal injury has been reported to be the owners’ authority to act as agents for the owner in relation associated with abnormal prerace physical inspection findings to veterinary matters). The information was maintained in (26, 35), previous number of injuries, being scratched or having confidence under the relevant law, including, but not limited beenonthevetlist(23), and with administration of non-steroidal to, the “official information privilege” (California Evidence Code anti-inflammatory drugs (NSAIDS) or corticosteroids (36, 37). section 1040) and the “veterinary services privilege” (California Despite this long list of risk factors, factors related to history of Business and Professions Code section 4857). Closed-ended lameness, administration of all types of medication, and surgery multiple-choice and categorical questions were primarily used have yet to be identified. in the three sections: lameness history, medication history, and To obtain information on these factors, attending surgery history. Open-ended text fields were included at the end veterinarians of horses that experienced a CMI, and of of each section to obtain more detailed information. control horses (horses that competed in the same race or trained The attending veterinarians of the case and control racehorses on the same day as their respective case but did not have a were invited to voluntarily complete the online veterinary fatal injury), were invited to complete an online veterinary medical history survey. The individual survey links were medical history survey. The aim of this survey was to identify distributed via email to the California Horse Racing Board information that can be used to aid in identification of horses at official veterinarians, who forwarded the email on to the relevant risk of catastrophic injury, and management factors that can be attending veterinarian of each racehorse. Reminders were issued modified to reduce this risk in racehorses. by email to participants that did not respond within one month of the date of death of the case horse. The mean time taken to METHODS complete a survey,